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Contribution of Organic Aerosol to PM2.5 in Bogotá, Colombia
KAREN BALLESTEROS, Ricardo Morales Betancourt, Amy P. Sullivan, Universidad de los Andes
Abstract Number: 681
Working Group: Aerosol Chemistry
Abstract
Organic aerosol (OA) is one of the major components of fine atmospheric aerosol particles. Recent fields campaigns and simulations studies in Colombia have demonstrated a significant contribution of OA to urban and rural aerosols. In this work we focus on constraining the sources associated with OA and its precursors over the city of Bogotá, Colombia. We used PM2.5 chemical speciation data from field campaigns carried out during 2018 to evaluate the ability of a regional transport model to reproduce and explain the observed OA. The samples were collected at three sites during high- and low aerosol concentration seasons in the region. We used The Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) with two different chemical mechanisms and aerosol schemes, RACM/MADE-VBS and MOZART/MOSAIC, in conjunction with the detailed in-situ observations of chemical PM2.5 to analyze the seasonality of OA over in the city of Bogotá, and to establish the most relevant sources (local vs. regional) for this component. Simulations were carried out for the same periods were data is available, spanning a high biomass burning season (February 2018) and a low biomass burning season (September 2018). The temporal and spatial distribution of meteorological variables in are well captured by both model configurations. The two aerosol schemes utilized in this work reproduce the observed seasonal variations in aerosol concentration, with a difference between February and September of 10 µg/m3. However, when MOZART was used, modeled PM2.5 was 30% higher than in the RACM experiment. Both schemes show that unspeciated PM2.5 and OA are the most prevalent aerosol in the city, in agreement with field observations. SOA concentration dominates the OA fraction by 66% for RACM-MADE-VBS and 74% for MOZART-MOSAIC during February and 69% for RACM-MADE-VBS and 71% for MOZART-MOSAIC during September consistently showing that MOZART-MOSAIC simulates more SOA than RACM-MADE-VBS. This differences between SOA within mechanisms may be attributed to MOZART-MOSAIC contains a simple SOA gas/particle partitioning scheme and has more biogenic specifies included.